Araceli Samaniego-Herrera

Invasive mammal eradication on islands results in substantial conservation gains.

Significance Global conservation actions to prevent or slow extinctions and protect biodiversity are costly. However, few conservation actions have been evaluated for their efficacy globally, hampering the prioritization of conservation actions. Islands are key areas for biodiversity conservation because they are home to more than 15% of terrestrial species and more than one-third of critically endangered species; nearly two-thirds of recent extinctions were of island species. This research quantifies the benefits to native island fauna of removing invasive mammals from islands. Our results highlight the importance of this conservation measure for protecting the worlds most threatened species. More than US

High-impact Conservation: Invasive Mammal Eradications from the Islands of Western Mexico

21 billion is spent annually on biodiversity conservation. Despite their importance for preventing or slowing extinctions and preserving biodiversity, conservation interventions are rarely assessed systematically for their global impact. Islands house a disproportionately higher amount of biodiversity compared with mainlands, much of which is highly threatened with extinction. Indeed, island species make up nearly two-thirds of recent extinctions. Islands therefore are critical targets of conservation. We used an extensive literature and database review paired with expert interviews to estimate the global benefits of an increasingly used conservation action to stem biodiversity loss: eradication of invasive mammals on islands. We found 236 native terrestrial insular faunal species (596 populations) that benefitted through positive demographic and/or distributional responses from 251 eradications of invasive mammals on 181 islands. Seven native species (eight populations) were negatively impacted by invasive mammal eradication. Four threatened species had their International Union for the Conservation of Nature (IUCN) Red List extinction-risk categories reduced as a direct result of invasive mammal eradication, and no species moved to a higher extinction-risk category. We predict that 107 highly threatened birds, mammals, and reptiles on the IUCN Red List—6% of all these highly threatened species—likely have benefitted from invasive mammal eradications on islands. Because monitoring of eradication outcomes is sporadic and limited, the impacts of global eradications are likely greater than we report here. Our results highlight the importance of invasive mammal eradication on islands for protecting the worlds most imperiled fauna.

Land crabs (Decapoda, Brachyura, Gecarcinidae) on Isabel Island, Mexico, including a new record, and its relation to the removal of invasive rats

Abstract Islands harbor a disproportionate amount of the earths biodiversity, but a significant portion has been lost due in large part to the impacts of invasive mammals. Fortunately, invasive mammals can be routinely removed from islands, providing a powerful tool to prevent extinctions and restore ecosystems. Given that invasive mammals are still present on more than 80% of the worlds major islands groups and remain a premier threat to the earths biodiversity, it is important to disseminate replicable, scaleable models to eradicate invasive mammals from islands. We report on a successful model from western México during the past decade. A collaborative effort between nongovernmental organizations, academic biologists, Mexican government agencies, and local individuals has resulted in major restoration efforts in three island archipelagos. Forty-two populations of invasive mammals have been eradicated from 26 islands. For a cost of USD 21 615 per colony and USD 49 370 per taxon, 201 seabird colonies and 88 endemic terrestrial taxa have been protected, respectively. These conservation successes are a result of an operational model with three main components: i) a tri-national collaboration that integrates research, prioritization, financing, public education, policy work, capacity building, conservation action, monitoring, and evaluation; ii) proactive and dedicated natural resource management agencies; and iii) effective partnerships with academic researchers in México and the United States. What is now needed is a detailed plan to eradicate invasive mammals from the remaining islands in the region that integrates the needed additional financing, capacity, technical advances, and policy issues. Island conservation in western México provides an effective approach that can be readily applied to other archipelagos where conservation efforts have been limited.

WESTERN HARVEST MOUSE, REITHRODONTOMYS MEGALOTIS (RODENTIA: MURIDAE), ON MAGDALENA ISLAND, MEXICO

Isabel Island, located in the mouth of the Gulf of California, Mexico, is a National Park. It supports a rich biodiversity and is internationally recognized as an important seabird breeding site (RAMSAR, 2011). Until 2008 two species of land crabs were common and widespread: the anomuran hermit crab Coenobita compressus (H. Milne Edwards, 1837) (cf. Guillén, 1992; Osorno et al., 1998) and the brachyuran red land crab Johngarthia planata (Stimpson, 1860) (cf. Rathbun, 1899; A. Samaniego, pers. obs.), the latter formerly referred to as Gecarcinus planatus before 2008 (Ng et al., 2008). As part of a long term restoration project, a baseline monitoring including several species of vertebrates as well as land crabs began in 2007 aiming to (a) develop an eradication plan for the invasive ship rat Rattus rattus (Linnaeus, 1978) and (b) assess the status of the insular ecosystem in order to compare it with a later condition after the rat eradication. Species to be monitored were chosen based on potential vulnerability to rat presence (Towns et al., 2006) and potential interference with eradication procedures (Wegmann, 2008; Varnham, 2010). Land crabs met both criteria. A successful rat eradication operation was conducted in May 2009 (Samaniego-Herrera et al., 2010); post-eradication monitoring of native fauna continued until September 2011. Here we update the list of land crabs for this island, include a new record, and describe changes in their population abundance regarding both, year seasonality and time after the eradication of an invasive predator, the ship rat.

The Conservation and Restoration of the Mexican Islands, a Successful Comprehensive and Collaborative Approach Relevant for Global Biodiversity

Abstract We collected two specimens of Reithrodontomys megalotis on Magdalena Island on the Pacific Ocean side of Baja California Sur. They represent the first insular record of the species in Mexico. These records extend the distribution range of the species about 450 km south of the southernmost record of R. megalotis in Baja California. In addition, three previously unpublished localities in mainland Baja California are reported.

Rodent eradications as ecosystem experiments: a case study from the Mexican tropics

Islands are biodiversity hotspots that offer unique opportunities for applied restoration techniques that have proven to bring inspiring outcomes. The trajectory of island restoration in Mexico is full of positive results that include (1) the removal of 60 invasive mammal populations from 39 islands, (2) the identification of conservation and restoration priorities, (3) the active restoration of seabird breeding colonies through avant-garde social attraction techniques, (4) the active restoration of integrated plant communities focusing on a landscape level, (5) applied research and science-based decision-making for the management of invasive alien species, (6) the legal protection of all Mexican islands, and (7) biosecurity and environmental learning programs to ensure outcomes are long lasting. Still, there are many complex challenges to face in order to achieve the goal of having all Mexican islands free of invasive mammals by 2030.

The Island Conservation NGO: some important clarifications

For effective and efficient pest management it is essential to understand the ecology of the target species and recipient ecosystems. The use of rodent eradication as a restoration tool is well established in temperate regions, but less common in the tropics, presenting an opportunity to undertake scientific learning in tandem with rodent eradications. On a dry tropical archipelago, we used a Before-After-Control-Impact framework to document (1) fluctuations in the abundance and demography of invasive Rattus rattus and Mus musculus on three different islands, (2) the trophic niche of all three invasive rodent populations, and (3) changes in the invertebrate community before and after rodent eradication, also comparing with two rodent free islands. While rat density was high and relatively stable throughout the year, the two mouse populations greatly differed in body size and seasonal dynamics, despite their proximity. The rodents in all three populations were generalist and opportunistic feeders, although stable isotope analyses results indicated major differences among them, driven by food availability and rodent species. Seasonal fluctuations in invertebrate communities depended on rodent invasion status, but recovery in the invertebrate communities one year after rodent removal was limited for all islands. Predictions for other tropical ecosystem biomes require long-term research on more tropical islands. Improving our understanding of island and species-specific contexts of rodent eradications can advance island restoration projects and assist the selection of indicator species for ecosystem recovery.

Best practice guidelines for rat eradication on tropical islands

This comment draws attention to some of the contents in the paper of Tershy et al. (Biodivers Conserv 21:957–965, 2012) concerning the work of Island Conservation, an NGO. In particular, it clarifies and explains the role of partnerships with other bodies in the restoration and other work of the NGO. We point out that the Mexican Grupo de Ecología y Conservación de Islas had a major role in the execution of much of the work reported on by Tershy et al.